Conversion of hydrocarbon oils



Patented Jan. 27, 1942 amen CONVERSION OF HYDRO'CARBON OILS Charles L. Thomas and Jacob Elston Ahlberg,

Chicago, Ill., assig'nors to ucts Company, Chicago, 11L,

Delaware Universal Oil Proda corporation of No Drawing. Application January 6, 1941, Serial N0. 373,309

16 Claims.

This is a continuation-in-part of our co-p'ending application Serial No. 176,648 filed November 26, 1937, which has matured into Patent 2,229,353.

This invention relates to hydrocarbon fractions produced in distilling petroleum oils and especially those of a distillate character which are vaporizable without substantial decomposition.

In a more specific sense the invention is concerned with-a modification of hydrocarbon oil conversion processes involving the use of particular and specific types of catalysts which function to selectively promote the formation'of low boiling gasoline fractions.

The art of cracking relatively heavy hydrocarbons to produce primarily gasoline or gas is very extensive and it is recognized that most of the basis principles of hydrocarbon decomposition are known and that particular commercial processes have been developed which embody these principles. The application of catalysts, however, in cracking reactions is practically upon the same basis as it is in other fields, that is, there is much more to be learned about them. A considerable number of the catalysts developed for cracking have a tendency to accelerate reactions the conversion ofleading to the formation of gas rather than of v gasoline, this being particularly evidenced by reduced metal catalysts such as nickel or iron and many of such catalysts aresensitive to sulfur poisoning and are quickly coated with carbonaceous materials which render them practically inert. This deposition of carbonaceous materials is many times related to the type of decomposition reactions selectively fostered by the catalyst.

The present invention is concerned with the use of catalytic materials which are specially adapted to accelerate the cracking of heavy distillate fractions of petroleum and other hydrocarbonaceous materials to increase the rate of production of high antiknock gasoline-boiling range fractions and gaseous by-products which contain unusually high percentages of readily polymerizable olefins which are a potential source of further gasoline yields. The preferred catalysts for the process are characterized by selectivity in accelerating gasoline-forming reactions rather than light gas-forming reactions by their selectivity in producing high antiknock gasoline, by their refractory character which enables them to retain their catalytic properties under severe conditions of temperature and pressure. by their ease and simplicity of manufacture and their exact reproducibility.

In one specific embodiment the present in- 'vention comprises a method for converting hydrocarbon distillate fractions containing substantially no gasoline into material yields of gasoline and gases containing relatively high per:- centages of polymerizableolefins by subjecting the vapors of such distillates at elevated temperatures and. substantially atmospheric pressure to contact with, granular silica-alumina catalysts prepared by special methods of precipitation and/or mixing and further treated by special washes to remove substantially all alkali metal ions and calcined at elevated temperatures to produce highly refractory alumina-silica particles which are able to withstand for long periods of time the-alternate service and reactivation periods.

We have found that the alumina-silica catalysts whose use characterizes the present cracking process and which may be prepared by several alternate methods described in more detail in succeeding paragraphs are rendered much more active and selective in accelerating gasolineforming reactions in cracking when the originally precipitated hydrated alumina and hydrated silica which go to form the primary composites in various proportions are completely freed from alkali metal ions which in most instances will be sodium ions because the sodium salts of silicic acids are cheapest and most readily available for the manufacture of this type of catalyst. The primary step in the method of preparing the catalysts whose use in cracking characterizes the an alkali metal silicate to precipitate a silica gel.

acid which is insuflicient In the case of alumina the desired hydroxide may be precipitated by the addition of alkalis, particularly ammonium hydroxide although other precipitants such as ammonium carbonate, ammonium hydrosulfide or ammonium sulfide may be employed.

- 3. A separately precipitated may be added to an aqueous solution of an aluminum salt and the hydrated alumina preeipitated in the presence of the suspended silica by the addition of alkaline precipitants.

4. A separately precipitated hydrated alumina may be added to an alkali metal silicate and the silica precipitated in the presence of the alumina by the addition of just the required amount of to redissolve the alumina.

hydrated silica ions.

mary hydrated silica with sufficient quantities It can be seen from the above that any method of obtaining a primary mix of hydrated silica and hydrated alumina maybe employed within the scope of the invention although obviously the character and .efilciency of the ultimately prepared alumina-silica masses will vary somewhat with the exact conditions of precipitation and the ratio of alumina to silica. For example, one proportion may furnish catalysts better for use in reforming a certain gasoline boiling range material, another'may be better for use in the cracking of a gas-oil distillate and still another may be better adapted to cracking still heavier fractions.

' An important feature of the present invention resides in the fact that cracking operations, particularly in petroleum distillates, may be conducted with greatly increased efiiciency when silica-alumina catalysts are employed which have been subjected to treatment to effect substantially complete removal of alkali metal ions from the primary hydrated alumina-silica masses prior to their calcining to prepare them for service. .It is not known whether the alkali metal salts such as sodium are present in the-primary hydrated composites in chemical combination or in an adsorbed state but it has been definitely determined that their removal is necessary if catalysts of superior value in accelerating cracking reactions are to be obtained. It is probable that the presence of these alkali metal ions causes a sintering or fusion of the surfaces of the primary composites during the heating period so that the porosity of the catalyst particles is much reduced, with a corresponding reduction in ef-' fective surface, considering the catalytic effects to be due at least in part to surface action. However, such concepts are principally speculations in view of the difiiculty of obtaining direct confirmatory evidence.

In preparing catalyst for the process several alternative methods are' available applicable to different primary hydrated silica-hydrated alumina composites to insure the substantially complete absence of sodium or other alkali metal One method consists in washing the priof hydrochloric acid to extract alkali metal by the formation of chlorides and possibly introduce hydrogen into the catalyst composites. Thus a precipitated hydrated silica mass may be first washed by decantation with water and filtered by pressure or suction to remove the major portion of the soluble impurities. The precipitate is then-removed fromthe filter and treated with relatively dilute hydrochloric acid, washed any'necessary number of times and again transferred to a pressure or suction filter and freed from. the major portion of the adhering water. As an alternative method for removal of alkali metals which may be present in the chemicallycombined or adsorbed condition, the precipitated silica may be washed with solutions of ammonium chloride which apparently serves to replace sodium with ammonium, which is later .volatilized in the drying and calcining of the silica either before or after admixture with the alumina. The desired amount of hydrated alumina may be precipitated on the siliceous material or-freshly precipitated'hydrated alumina may be added and mechanically mixed therewith.

Another method rwhich has been found to be efficacious in the preparation of cracking cata- 1 lysts consists in washing the primary hydrated so doing. As a variation of this method the coprecipitation or mixing of the primary hydrated silica and alumina may be brought about in the presence of ammonium hydroxide or any of the other salts of ammonium already mentioned in sufiicientexcess to insure an adequate removal of the alkali metal ion. In the case v of coprecipitation it has been found that the necessary excess of ammonia is present at the point corresponding to a sufiicient coagulation of the gel structure of the primary precipitates to permit ready filtering and washing. In other words if suflicient ammonia has been used to insure easy washing and filtering the alkali metal salts have been generally reduced to a point at which they no longer have any appreciable adverse influence in the primary hydrated silica precipitates or the silica-alumina masses indicates that the alkali metals are held by adsorption rather than by chemical bonds. This is indicated by the fact that the alkali metal ions are replaceable by ammonium or multivalent positive ions which are known in general to be more strongly adsorbed than alkali metal ions. This differentiates this replacement from that occurring in the case of zeolites.

A still further alternative method of removing alkali metal salts from freshly precipitated hydrated silica or alumina-silica composites consists in treating such composites with salts of metals which can replace the sodium in a similar manner to that described in the case of ammonium chloride. For example, a primary comnum,.magnesium, calcium, manganese, cerium,,.

or other multivalent metals in which the metal forms the positive ion of the salt being used.

As a further example, the washing may first be with an acid solution and an ammonium salt solution as above described preliminary to treating with solutions of the multivalent salt solutions. Obviously such replacements may be allowed to proceed with consequent variation in the properties of the final catalyst. This method of operation permits the production of catalysts of a high degree of variability which are obviously non-equivalent in regard to their effect upon a given cracking reaction.

After a final washing of the hydrated aluminasilica mix, it is recovered as a filter cake by using any known type of suction or pressure filter and is then heated toa temperature of the order of 300 F. for a period of 36 to 48 hours after which it may be ground and sized to recover particles of a convenient average diameter or formed into any desiredshapes by compression methods. .It has been found that the drying at 300 F. produces material having a total water content of about 15% by weight which as already stated apparently corresponds to the best workability of the material. By calcining at cracking temperatures of the order of approximately 850-1000 F., a further dehydration occurs so that for example after a considerable period of heating at 900 F.,

the water content as determined by analysis is of the order of 203% which is firmly fixed and does not appreciably vary either asthe result of long service or a large number of reactivations at considerably higher temperatures.

Catalysts prepared by the above general procedure evidently possess a large total contact surface corresponding to a high porosity, the pores being of such size that hydrocarbon oil vapors are able to penetrate to a considerable 1 relatively short and of the .order of 1-10 seconds.

distance and yet not so small that when the pores become clogged with carbonaceous deposits after a long period of service, they are difllcult to reactivate by oxidation. This structure is also retained after many alternate periods of use and reactivation as evidenced by the fact that the catalysts may be repeatedly reactivated by passair over the spent particles to burn off deposits of carbonaceous material at temperatures as high a 1400-1600 F. without material loss of catalytic activity.

According to the present process catalysts prepared by the general procedure described in the preceding paragraphs are utilized to the best advantage in cracking reactions when employed as filling material in tubes or chambers in the form of small pellets or granules. In the majority of cases wherein hydrocarbon fractions readily vaporizable at moderate temperatures without extensive decomposition are employed, the average particle size is within the range of 6-10 mesh, which may apply either to small liters of water.

pellets of uniform size and short cylindrical shape or to particles of irregular sizeand shape produced by the grinding and sizing of the partially dehydrated materials. While the simple method of preheating a given fraction of hydrocarbon oil "vapors to a temperature suitable for their crackmg in contact with the catalysts and then pass- I ing the vapors over a stationary mass of catalyst particles may be employed in'some cases, it is usually preferable to pass the preheated vapors through banks of relatively small diameter catalyst-containing tubes in multiple connection between headers, since this arrangement of apparatus is better adapted to permit exterior heating of the catalyst tubes to compensate for the heat loss in the endothermic cracking reactions.

After the passage of the oil vapors over the catalyst, the products may be. separated into material unsuitable for further cracking, intermediate insufliciently converted fractions amenableto further catalytic cracking, gasoline boiling range materials and gases, the intermediate fractions being returned directly to admixture with the charging stock so that ultimately there is complete recycling of all fractions and maximum,

utilization of the charging stock production.

The present process besides being characterfor gasoline ized by the use of novel catalysts is further char- .acter of gas oil, it is seldom necessary to employ temperatures greatly in excess of 950 F. in the 1 catalytic conversion zone.

pressure, it is seldom desirable to employ those' In the matter of materially above atmospheric except in so far as The following examples .of preparation and use of the types of catalysts peculiar to the present invention are given to indicate their novelty and utility in practical cracking processes although not for the purpose of limiting the'invention in exact agreementwith the data introduced. I

Example I l The method of catalyst preparation in' thi case isto mix an alkali metal silicate and an acid to forma hydrated silica, mixing the hydrated silica'with 'asolution of an aluminum salt and precipitating hydrated alumina and purifying the composite.

A solution is prepared containing 415 grams of water glass of approximately 40 Baunr in 5 molar hydrochloric acid is slowly added to the diluted water glass solution while stirring. The

silica hydrogel is filtered and washed with water and-then suspended in approximately 500 cc. of

water containing approximately 40 grams of aluminum chloride hexahydrate in solution. Ammonium hydroxide is'then added to precipitate the alumina hydrogel in the presence of the hydrated silica and the composite of hydrated alumina and hydrated silica is then washed with a solution containing approximately 20 grams per liter of magnesium chloride until the final washings are free from sodium when tested with a uran'yl acetate reagent. The purified catalyst preparation is then recovered as a filter cake which is dried at approximately 932 F; When granules of the above prepared catalyst are disposed in a catalyst chamber and contacted with a Pennsylvania gas oil which has been vaporized and preheated to a temperature of'932" F. and passed through the catalyst at an hourly liquid space velocity of approximately 4, the following results are obtained:

Data on cracking experiments Run #1 Run #2 897 Gasoline 400 F. E. P.:

Volume, er cent A.'P. 1.. F Octane number, motor method E. P., F Gases (boiling range below +l0 Weight, per cent (total). Molecular weight Bropene and butenes, weight percent of charge Gas oil recovered (recycle stock):

as a as assesses g N on me:-

Ezample II The procedure in preparing the catalyst in this example is to precipitate a hydrated silica by adding an acid to a water glass solution, washing the hydrated silica free from alkali metal ions and Approximately 500 cc. of 2.5

addition of ammonium hydroxide.

precipitating the hydrated alumina in the presence of the suspended purified hydrated silica by the addition of an alkaline precipitant free from alkali metal impurities.

About 415 grams of approximately 40 Baum water glass is diluted with 5 liters of water and approximately 500 cc. of 2.5 molar hydrochloric acid is added thereto gradually while stirring to precipitate a hydrated silica. The hydrated silica is washed several times with water and then with a solution containing approximately 25 grams of magnesium chloride per liter until the washings are free from sodium when testing with a uranyl acetate reagent. The purified silica hydrogel is then suspended in approximately 500 cc. of water containing 40 grams of aluminum chloride hexahydrate and hydrated alumina precipitated in the presence of the silica hydrogel by the The composite of hydrated silica and hydrated alumina is then recovered as a filter cake and dried at a temperature of approximately 275 F., The dried material is crushed to pass a 40 mesh screen, mixed with a lubricant and pilled to form -inch pellets. The pilled catalyst is calcined at a temperature of approximately 1500" F.

A Mid-Continent gas oil is vaporized and preheated to a temperature of approximately 932 F. and is contacted with the pelleted catalyst above described at substantially atmospheric pressure in a once-through operation. Approximately 23 per cent by volume of the charge of 400 F. end-point gasoline is produced having an octane number of 77.1 by the motor method.

We claim as our invention:

1. A process for converting hydrocarbon dis-- tillate heavier than gasoline into substantial lates heavier than gasoline into substantialyields of gasoline which comprises subjecting said distillates under cracking conditions to contact with a catalyst tree or alkali metal compounds and produced by separately precipitating hydrated or adsorbed alkali metal ions, mixing said separately produced precipitates in a wet condition,

. filtering and washing the precipitated '.material yields of gasoline which comprises subjecting said distillate under cracking conditions to contact with a catalyst produced by separately precipitating hydrated aluminum oxide and hydrated silicon dioxide containing alkali metal ions, freeing the precipitated materials of alkali metal ions, by treating with a solution of a salt of magnesium, mixing the purified materials in the wet condition, and drying to remove a major portion of the total water content.

2. A process for converting hydrocarbon distillates heavier than gasoline into substantial yields of gasoline which comprises subjecting said distillates under cracking conditions to contact .with a catalyst free of alkali metal compounds and produced by separately precipitating hydrated aluminum oxide and hydrated silicon di-, oxide containing alkali metal ions, mixing said separately produced precipitates in a wet condition, adding asuflicient quantity of'a magnesium compound to replace combined or adsorbed alkali metal ions present in'the precipitate with maga magnesium salt to a suspension of the hydrated silicon dioxide to replace combined or adsorbed alkali metal ions with magnesium, mixing said to substantially complete removal of soluble substances and heating the washed precipitate to remove the major portion of its total water content.

5. A process for converting hydrocarbon distillates heavier than gasoline into substantial yields of gasoline which comprises subjecting said distillates under cracking conditions to contact with a catalyst free or alkali metal compounds and produced by separately precipitating hydrated aluminum oxide from a solution of a sol- .uble 'aluminate and hydrated silicon dioxide by the acidification of alkali metal silicate solution,

mixing said separately produced precipitates in a wet condition, adding a sufllcient quantity or a magnesium salt to replace combined or adsorbed alkali metal ions present in the precipitate with magnesium, filtering and washing the precipitated' material to substantially complete removal of soluble substances and heating the washed precipitate toremove the major portion of the total water content.

6. A'process for converting hydrocarbon distillates heavier than gasoline into substantial yields of gasoline which comprises subjecting said distillate under cracking conditions to contact with a catalyst produced by precipitating hydrated aluminum oxide from an aqueous solution of a soluble aluminum compound, separately precipitating hydrated .silicon dioxide from an aqueous solution or an alkali metal silicate, combining the precipitates in undried condition and removing from the hydrated silicon dioxide alkali metal ions present therein as a result of its precipitation-from the alkali metal silicate solution by washing with a solution of a magnesium salt, and calcining the commingled precipitates.

'7. A conversion process which comprises contacting normally liquid hydrocarbon oil under cracking conditions with a catalyst produced by precipitating hydrated silicon dioxide containing alkali metal ions, precipitating hydrated aluminum oxide,.treating resultant precipitated material, containing said alkali metal ions, with an aqueous solution of a magnesium compound and"- combining the precipitated aluminum oxide and silicon dioxide in undried condition, and drying the mixture to remove the major portion of its water content. I

8. The process as defined. in claim 7 further characterized in that the hydrated aluminum oxide is substantially free of alkali metal ions and the hydrated silicon dioxide is treated with said solution prior to combining it with the hydrated aluminum oxide, the latter being precipitated in the presence of-the hydrated silicon dioxide.

characterized in that the aluminum oxide and silicon dioxide are co-precipitated and the admixed precipitates treated with said solution.

10. The process as defined in claim 7 further characterized in that the aluminum oxide and silicon dioxide are precipitated independently of each other.

11. The process as defined in claim 7 further characterized in that said oil is a distillate heavier than gasoline. 1

12. A conversion process which comprises subjecting the hydrocarbon oil to cracking conditions in the presence of a calcined mixture of separately precipitated alumina hydrogei and silica hydrogel, said hydrogels having been combined in undried condition prior to the calcination and said silica hydrogel having been substantially freed of alkali metal compounds by washing with a solution of a salt of magnesium.

13. The process as defined in claim 12 further characterized in that the silica hydrogel is precipitated prior to the alumina hydrogel and the latter thereafter precipitated in the presence of the silica hydrogel.

14. The process as defined in claim 12 further characterized in that the silica hydrogel is precipitated prior to the alumina hydrogel and suspended in an aqueous aluminum salt solution, the alumina hydrogel beingcombined with the silica hydrogel by precipitating the same from said solution in the presence of the silica hydrogel.

15. A conversion process which comprises con-- tacting normally liquid hydrocarbon oil under cracking conditions with a catalyst produced by precipitating hydrated silicon dioxide containing alkali metal ions, precipitating hydrated aluminum oxide, treating resultant precipitated ma- 'terial containing said alkali metal ions with an aqueous acid solution and with a solution of a magnesium salt to remove alkali metal ions and combining the precipitated aluminum oxide and silicon dioxide in undried condition, and drying the mixture to remove a major portion oi its 

